Study Of(10,100) GeV Gamma-ray Bursts With Double Shower Front Event From ARGO-YBJ

Gamma-Ray Bursts(GRBs),is one of the important physical targets of ARGO-YBJ experiments,has always been a hot topic in astronomy.Since the discovery of GRBs by Vela satellite for the first time in 1967,a large number of satellite detectors and ground experiments have been continuously added to the study of GRBs.Up to now over 5000 GRBs with gamma rays of energies from keV to MeV have been observed by dedicated satellites,of which about 500 redshift have been measured.These data confirm that most GRBs indeed originate at cosmological distances.Are all GRBs originating from cosmological distance? Is there GRBs originating in the Milky Way?Satellite experiments are limited by the receiving area and manufacturing cost in space conditions,the GRBs photons detected by satellite instruments are mostly in the keV-MeV energy range.The search for high energy GRBs can provide information for the lower limit of GRBs source distance.About 80 GRBs detected by satellite-based experiments such as The EGRET and Fermi-LAT,have been detected to contain photons with energy above 1 GeV.It shows that the energy spectrum of GRBs can extend to GeV and above energy regions.ARGO-YBJ experiments is the first time in the world to use the full coverage of the RPC “carpet” array.By using double shower front events,the primary energy threshold of the ARGO-YBJ detector can be lowered to a few tens of Ge V.The lower energy threshold is effectively connected with the Fermi satellite,and the advantages of the all-weather and large field of view which is unique to the EAS array,The “double shower front” events has unique advantages in the detection of high energy GRBs.This paper mainly focuses on the photon radiation with 10-100 GeV energy region around the double shower front events.The following are mainly done.Firstly,The “double shower front” event in the ARGO-YBJ experiment was reconstructed,and the characteristics of this type of event were analyzed.Then,The background estimation in the GRBs search is optimized.To find photon signals in a large number of cosmic ray events,the background event rate must be correctly estimated.Due to the rotation of the earth,the zenith angle varies with time.This part focuses on the analysis of the change of zenith angle in the duration of the long GRBs,so that the background estimation is more accurate.In addition,The ARGO-YBJ sensitivity in detecting gamma-ray bursts(GRBs)by using double shower front events is also studied for various cutoff energies,time durations,and zenith angles of GRBs in ARGO's field of view.Finally,A search for 10-100 GeV burst-like events in coincidence with GRBs detected by Fermi satellite was done using the “double shower front” events of the ARGO-YBJ experimentand.It is regrettable that in these searches,no significant signal has been detected.It can be seen that the sensitivity of the ARGO-YBJ experiment to detect GRBs is not sufficient,and the more sensitive LHAASO experiments under construction are expected to achieve breakthrough results in the search for GRBs.